Recent content by cruff

Yes, that appears suitable. Here is a link to a good description of what the X and Y capacitor classes mean. https://www.allaboutcircuits.com/technical-articles/safety-capacitor-class-x-and-class-y-capacitors/

Yes it is okay to use a higher voltage rating replacement. If the replacement for the Y type caps are also Y type caps then you can use a different type. If the ceramic capacitor is not Y rated then you can not use it as a replacement. Since you didn't specify the manufacturer's capacitor...

If you aren't implementing/supporting the SCSI disconnect/reconnect feature then the controller really doesn't need an ID for itself.

The supply voltages look to be within normal tolerances, note that until there was some load the secondary supply voltages (i.e. everything that isn't +5 V) weren't quite as close, but under load they end up being more close to the targets. Your problem lies elsewhere, possibly with some bad...

The first way is to disconnect the power supply and use a meter to check the unloaded voltages by probing the pins of the connector from the side that connects to the pins on the motherboard. The second is to probe the rear of the connector while it is under load while attached to the...

Also consider reseating the chips that are in DIP sockets. You might also press on the VSC leadless chip at UH2 to make sure it is seated (that style chip really needs the purpose built chip extractor to safely remove it). Also if you haven't already done so, reseat any interface cards and...

Verify that the power supply voltages are within tolerance. Also look if the clock battery that has leaked over the PCB. Which revision IIgs do you have?

Are you positive you have the polarized capacitors installed in the correct orientation? Does it display an error code?

Your tantalum capacitor likely just failed itself, it's a known issue. The bugs had nothing to do with it unless they left corrosive fluid on the circuit board that contributed to the failure condition.

Is it 50/60 Hz hum? Maybe you have other bad solder connections, possibly on the ground plane or a marginal filter capacitor on the primary side of the switching power supply.

BTW, if you go the Quadra route to run A/UX, don't get a 631 or other model that has an IDE drive instead of SCSI. A/UX doesn't support IDE drives out of the box. Not sure if anyone ever made a mod to A/UX to support one.

I have fond memories of the IIsi I had. I remember the 20 MB drive I bought for it cost about $900. I had A/UX running on it along side Mac OS. It was definitely a nice size machine for that era.

The pin outs of the 8530 chip would not change, unless they substituted another variant. If you don't have it, this appears to be the ROM 03 schematic https://downloads.reactivemicro.com/Apple%20II%20Items/Hardware/IIgs/Schematic/, which is formatted differently to the ROM 01 schematic I have.

The SCC diagnostic test performs a exhaustive test of all the values that can be written to the SCC register 2 (interrupt vector, via channel A only), registers 12 and 13 (the baud rate generator counter registers) and register 15 (the external status/interrupt control register, bits 7, 6, 5, 4...

It is the Y2 crystal. It is the baud rate clock (SYNC.L, RTXCA.L, RTXCB.L), and the PCLK signal (CREF.H from the Mega 2 chip) provides the timing signal for the remainder of the 8530 operation, which includes the read/write of the 8530 internal registers. Thus if PCLK is good but the baud rate...